A turbomachine, in particular a gas turbine, comprises a turbine in which a hot gas is expanded for attaining a mechanical work, after the hot gas had been compressed in a compressor and heated up in a combustion chamber. For a high mass flow rate and therefore for a high power of the gas turbine the latter is designed as an axial gas turbine, wherein the turbine comprises a plurality of consecutive blade rings. The blade rings comprise alternately guide vanes attached to the housing of the gas turbine and rotor blades attached to a rotor of the gas turbine. Guide vanes and/or rotor blades can be referred to as blading. A single vane or guide vane or a single blade or rotor blade is also called airfoil as a more general term.
The higher the inlet temperature of the hot gas is in the turbine the higher is the thermodynamic efficiency of the gas turbine. The maximal acceptable inlet temperature is limited because of the limited thermal resilience of the turbine blading. It is desirable to design a turbine blading which can cope with a high thermal load but it must have a sufficient mechanical stability. Conventional turbine bladings comprise materials or combinations of materials which allow only part of the potential for raising the thermal efficiency of the gas turbine. For a further rise of the inlet temperature it is known to cool the turbine blading, so that it is subjected to a lower thermal load due to the hot gas than it would be without the cooling.
A turbine airfoil is described in EP 1 327 747 A2, wherein cooling air is flowed inside the airfoil.